Technical Abstract:
Grapefruit juice (GFJ) interferes with the cytochrome P450 3A4 activity responsible for metabolizing certain medications, and it is the furanocoumarins (FCs) in GFJ that have been shown to be the main compounds which cause these interactions. We previously found that a number of foods sequester FCs in GFJ. To further investigate this binding phenomenon, we attempted to remove different macromolecules from corn through various extraction methods and determined whether the remaining biomass can sequester two major FCs, 6', 7'-dihydroxybergamottin (DHB) and bergamottin (BM) in GFJ. When most lipids were removed by a series of chloroform:methanol (2:1) and hexane:isopropanol (3:2) extractions, the resulting corn powder (fraction 1, Figure 1) still sequestered FCs in GFJ, indicating that components responsible for the binding are still present in the fraction 1. However, when water-soluble compounds were further removed from the fraction 1 (fraction 2, Figure 1), the binding phenomenon of DHB to the fraction 2 completely disappeared but BM binding still largely occurred. The results suggest that the components interacting with DHB are hydrophilic. Furthermore, the binding of BM to fraction 3 (acid or base hydrolysis of fraction 2, Figure 1) was completely abolished, suggesting that the components binding to BM could tightly link to other macromolecules (i.e. proteins or carbohydrates) within the fraction 2 but released by the hydrolysis. Our results show that BM and DHB differentially bind to components of corn.